Return flow carburetor



Dec. 14, 1965 T. M. BALL 3,223,392

RETURN FLOW CARBURE'I'OR Original Filed July 28, 1959 INVEN TOR.77%477746' Mid/Z BY n q/AZW United States Patent 3,223,392 RETURN FLGW(ZAREURETGR Thomas M. Ball, Bloomfield Hills, Mich, assignor to ChryslerCorporation, Highland Park, Mich, a corporation of Delaware ()riginalapplication July 28, 1959, Ser. No. 830,007, new Patent No. 3,161,700,dated Dec. 15, 1964. Divided and this application dune 15, 1964, Ser.No. 381,279

4 Q'Jlaims. (Cl. 261l27) This invention relates to improvements in acarburetor particularly adapted for use with an automobile internalcombustion engine. This application is a division of copendingapplication, Serial Number 830,007, filed July 28, 1959, now PatentNumber 3,161,700, issued December 15, 1964.

In conventional carburetors, a fioat controlled fuel inlet needle valveis employed to regulate the fuel level in the carburetor fuel bowl.Small dirt particles sometimes interfere with effective operation of thevalve, as for example by becoming lodged between mating valve seatswhich otherwise cooperate to regulate the fuel flow into the fuel bowl.Also the floats require considerable size in order to be effectivebecause of the comparatively low specific gravity of the fuel. Inconsequence the size of the fuel bowl must be appreciably larger than isotherwise desired.

An important object of the present invention is to provide an improvedcarburetor which avoids the fore going objections and in particular toprovide a floatless carburetor which does not require a fuel inletneedle valve.

Another object is to provide such a construction including an overflowstandpipe in the fuel bowl having an upper opening which determines themaximum fuel level in the bowl. A fuel inlet pump is provided to pumpfuel into the bowl at a rate in excess of demand. The excess fueloverflows into the standpi-pe and is returned to the fuel tank. In orderto overcome adverse grade conditions which prevent the excess fuel fromreturning to the tank by gravity flow, a scavenging pump is provided inthe fuel return line between the overflow standpipe and the tank.

Among other advantages of the above structure, elimination of thenecessarily large float enables utilization of a comparatively smallfuel bowl closely adjacent the inlet air induction conduits of amultiple barrel carburetor, for example. The small fuel bowl thuslocated is less sensitive to grade and inertial effects and enablesuniform fuel distribution to each of the several induction conduits.Also recirculation of the fuel drives off its more volatile fuelfractions and thereby minimizes some of the problems of the conventionalfloat controlled carburetor, as for example those concerned with vaporformation.

In order to provide adequate fuel during maximum engine speed at wideopen throttle, a fuel inlet pump is provided which delivers an excesssupply of fuel to the fuel bowl during all operating conditions of theengine. When the throttle is suddenly closed while the engine is stilloperating at high speed, unless some provision is made to the contrary,a major portion of the fuel supplied to the fuel bowl will berecirculated. In general the life of a fuel pump and in particular thelife of an engine driven diaphragm type pump, which is preferred forsupplying fuel in the quantity required and at a substantially uniformpressure regardless of changes in engine speed, depends upon thequantity of fuel pumped.

For the above reasons, as well as the desirability of conserving powerin an automobile engine and of minimizing fuel heating by excessiverecirculation, another object of the present invention is to provideimproved simple and highly effective means for supplying fuel to thefuel bowl in reasonable and safe amounts related to engine requirements.

Another object is to provide a carburetor and diaphragm fuel pumpcombination of the type described wherein the pump comprises a pumpingchamber having a movable diaphragm defining one wall thereof. Thepumping chamber is provided with check valve controlled inlet anddischarge ports in communication with a fuel tank and with the fuel bowlrespectively and operative so that during movement of the diaphragm inone direction in an intake stroke to enlarge the volume of the pumpingchamber, fuel is drawn from the tank into the pumping chamber. Duringmovement of the diaphragm in the opposite direction in a pumping stroke,fuel is discharged from the pumping chamber into the fuel bowl. Thediaphragm is secured to a plunger arm for actuation thereby. A pumpingspring under compression between the diaphragm and a fixed portion ofthe pump mechanism yieldingly urges the diaphragm in said oppositedirection to cause the pumping stroke. A pivotal arm engageable with arotating cam driven by the automobile engine to be pivotally oscillatedthereby is also engageable with the plunger to move the latter in saidone direction against the force of the pumping spring to compress thelatter. The pivotal arm is also freely engageable with the plunger sothat during the reverse pivotal movement of the arm, the latter willmove independently of the plunger and release the diaphragm for springurged pumping movement in said opposite direction, but will notpositively urge movement of the diaphragm in said opposite direction. Inconsequence, the pumping force will result entirely from the compressedpumping spring and will be substantially constant regardless of thespeed of the engine or of the pivotally oscillated arm.

Other and more specific objects are to provide such a diaphragm pump andcarburetor combination having means for varying the pumping stroke ofthe diaphragm in said opposite direction by a direct linkage with thethrottle actuating mechanism, or by pressure actuated means connectedwith the engine air inlet induction system or with the discharge side ofthe scavenging pump.

Other objects of this invention will appear in the following descriptionand appended claims, reference being bad to the accompanying drawingsforming a part of this specification wherein like reference charactersdesignate corresponding parts in the several views.

FIGURE 1 is a schematic mid-sectional view of a floatless return flowcarburetor and pump embodying the present invention showing generalmeans actuated by the throttle valve for controlling the diaphragmpumping stroke.

FIGURE 2 is a view similar to FIGURE 1 but showing a specific mechanicallinkage with the throtle mechanism for controlling the diaphragm stroke.

FIGURE 3 is a view similar to FIGURE 2 illustrating a modification.

It is to be understood that the invention is not limited in itsapplication to the details of construction and arrangement of partsillustrated in the accompanying drawings, since the invention is capableof other embodiments and of being practiced or carried out in variousways. Also it is to be understood that the phraseology or terminologyemployed herein is for the purpose of description and not of limitation.

Referring to FIGURE 1, the carburetor shown comprises a cast housingformed to provide an air inlet induction conduit including a venturiportion 10 having a restricted venturi 11 at its upper portion and athrottle blade 12 pivotally mounted on a shaft 13 at a lower portionusually referred to as the throttle body. An upper portion of thecasting is formed to provide an air horn 14 adapted to be connected withthe usual air filter and opening at its downstream end into the venturi11 to supply air J thereto. The casting portions and 14 are suitablysecured together, as for example by screws not shown, and comprise anupper portion of the air inlet and fuel mixing induction system whichextends downstream of the throttle valve 12 and discharges into the dualengine cylinders in a conventional manner.

Integral with the casting 10 in the present instance is a fuel bowlcasting 15 containing an annular chamber or fuel bowl 16 enclosing acylindrical standpipe or weir 17 which also serves as an accelerationpump cylinder containing a plunger 18 reciprocable in its lower portionand secured to a plunger shaft 19 for actuation thereby. Where desiredthe shaft 19 is connected by suitable linkage with a pedal operatedaccelerator mechanism which controls the opening and closing of valve 12to operate conjointly therewith. Upon upward movement of plunger 18,fuel is drawn into the lower portion of chamber 17 via conduit 20 incommunication with the bowl 16. A suitable check valve illustratedschematically as a ball check element 21 normally seats at the mouth ofthe duct 20 opening into the lower portion of chamber 17 to prevent lossof fuel therefrom but is raised from its seat by the fuel flow intochamber 17 on the upstroke of plunger 18. Upon downward movement ofplunger 18 the fuel is forced from chamber 17 into the induction conduitvia acceleration fuel conduit 22, ball check valve 23, and nozzle 24which latter discharges into the induction conduit at a locationimmediately above the throat of venturi 11. The check valve 23 isschematically illustrated as a ball normally urged by a spring to aseated position closing nozzle 24 from the interior of chamber 17, theball being readily movable upward against the tension of its seatingspring by the acceleration fuel presssure upon downward movement ofplunger 18. The main fuel to the engine is supplied via duct 25 whichopens at its lower end through metering port 26 into the fuel bowl 16and communicates at its upper end with a fuel nozzle 27 having itsdischarge orifice located within the throat of venturi 11.

In accordance with the structure described thus far, fuel entering thebowl 16 in excess of engine requirements overflows the upper edge ofstandpipe 17 which thereby maintains the fuel in the bowl 16 at apredetermined maximum level determined by the effective height of thestandpipe 17 without recourse to a float operated mechanism. Fuel issupplied to the bowl 16 from a suitable fuel tank via conduit 28.

A multiple piece fuel pump housing 37 comprising an upper dome 38 and alower basin 39 cooperate with diaphragms 40 and 41 respectively toprovide an inlet fuel pumping or working chamber 42 and an exhaust fuelpumping or scavenging chamber 43. Springs 44 and 45 under compressionbetween portions of housing 37 and diaphragms 40 and 41 respectivelyurge the former diaphragm upwardly and the latter diaphragm downwardlyto effect the pumping strokes for the respective chambers 42 and 43.

The upper working chamber 42 comprises a portion of supply duct 28 whichcommunicates upstream of chamber 42 with the fuel tank. Fuel enters andleaves chamber 42 via an inlet port 46 and a discharge port 47associated with check valves 48 and 49 respectively. Upon downwardmovement of diaphragm 40 as explained below, fuel is drawn in thedirection of the arrow 28a from the tank and through inlet port 46 intoworking chamber 42. During this operation ball valve 48 is forced fromits seat at port 46 by the fuel flow, and ball valve 49 seats at thedischarge port 47 to close the latter from the fuel bowl 16. Upon upwardmovement of diaphragm 40, ball valve 48 is caused to seat at port 46 toclose the working chamber 42 from the fuel tank. During this operation,the pressure exerted in chamber 42 unseats ball valve 49 from port 47and supplies fuel via conduit 28 to the fuel bowl 16. The spaces at thesides of the diaphragms 40 and 41 opposite chambers 42 and 43respectively are 4 vented to the atmosphere by ducts 50 and 51 tofacilitate the pump operation.

Fuel is returned in the direction of arrow 52a from standpipe 17 to thefuel tank via fuel return conduit 52 which includes chamber 43 as aportion thereof. Upstream, the conduit 52 communicates with standpipe 17at a location above the uppermost limit of movement of plunger 18. Thereturn fuel enters chamber 43 via port 53 and discharges from chamber 43via port 54. Ball check valves 55 and 56 are associated with ports 53and 54 respectively, so that upon upward movement of diaphragm 41 asdescribed below, ball 56 seats against port 54 to close chamber 43 fromthe fuel tank. During this operation, ball 55 is unseated from port 53to open communication between chamber 43 and standpipe 17 and to drawfuel from the latter. Upon downward movement of diaphragm 41, ball 55 isseated against port 53 to close chamber 43 from standpipe 17.Simultaneously ball 56 is unseated from port 54 by the pressure inchamber 43 to discharge fuel from the latter in the direction of arrow52a to the tank. Movement limiting pins in the conduits 28 and 52associated with the ball valves 48, 49, 55 and 56 prevent undue movementof the balls from their associated ports. Inasmuch as the check valvesare well known, these are merely shown schematically and are notdiscussed in further detail.

Actuation of the diaphragms 40 and 41 is accomplished by driving shafts57 and 58 connected to these diaphragms and terminating in enlargedheads 59 and 68 respectively. Pivotal levers 61 and 62 are pivoted onhousing 37 at locations 63 and 64 respectively between their ends. Eachlever has one end engaged with a rotating eccentric cam 65 mounted on ashaft 66 driven by the automobile engine. The opposite ends of thelevers 61 and 62 are provided with oversized openings 67 and 68 throughwhich the rods 57 and 58 extend freely to enable their relative slidingmovement with respect to the levers 61 and 62 until the levers engagethe enlarged heads 59 and 60.

Upon operation of the automobile engine, shaft 66 is rotated to turn cam65 and thereby cause pivoting of levers 61 or 62. Upon clockwisepivoting of lever 61, or counterclockwise pivoting of lever 62, the head59 or 60 is engaged to pull the associated rod 57 or 58 in the directionto compress the spring 44 or 45 as the case might be. Uponcounterclockwise pivoting of lever 61 and clockwise pivoting of lever62, the oversized openings 67 and 68 enable the levers to swingindependently of the shafts 57 and 58, whereupon springs 44 and 45 arereleased to force diaphragms 40 and 41 in pumping actions toward theassociated dome 38 and basin 39. The pivotal action of levers 61 and 62merely compresses the springs 44 and 45 alternately, which latter thenexert resilient force to effect the pumping action of the associateddiaphragms 40 and 41. In consequence, fuel is discharged from chamber 42at a uniform optimum pressure determined by the force of spring 44. Uponthe upward spring urged pumping stroke of diaphragm 40, fuel isdischarged via port 47 to fuel bowl 16. All fuel in excess of enginerequirements overflows the standpipe 17 and returns by conduit 52 tochamber 43 via port 53, whereupon the fuel is pumped to the fuel tank bydownward spring urged pumping movement of diaphragm 41.

In order to prevent too great an excess of fuel from being pumped tofuel bowl 16 when the engine is operating at comparatively light load,means are provided for limiting the maximum movement of diaphragm 40during the spring urged pumping stroke. As illustrated in FIG- URE 1,eccentric cam 69 is keyed to a pivot shaft 70 mounted within housing 37and extending to the exterior thereof. An operable connection betweencam 69 and throttle valve 12 is indicated by the broken line 71, wherebyupon closing of the throttle valve 12, cam 69 is rotated to limit themaximum upward pumping stroke of diaphragm 40, as described morespecifically in regard to FIGURES 2 and 3.

Thus with decreasing engine load, the pumping stroke of diaphragm 40 isdecreased, the fuel flow pumped via conduit 28 into fuel bowl 16 isdecreased, and recirculation of fuel to the bowl 16 is minimized. Withincreasing engine load, the increased pumping stroke enabled bydiaphragm 40 increases the fuel flow via conduit 28 to fuel bowl 16.

FIGURE 2 illustrates the return flow carburetor and pumping mechanism asin FIGURE 1 wherein corresponding parts are numbered the same.

A generally horizontal lever 83 is keyed at one end to a lateralexternal extension of cam shaft 70 which in turn is keyed to cam 69overlying diaphragm 49 as in FIG- URE 1. Cam 69 is disposed to enableincreased upward pumping movement of diaphragm 40 when lever 83 is swungclockwise about the axis of shaft 70. The left end of shaft 83 isprovided with a transverse pin 84 slidably secured within the yoke 85 ofa pivotal shaft 86 pivotally mounted between its ends at 87 to a fixedportion of the carburetor casting 15. The left end of shaft 86 ispivotally connected at 88 to the upper end of a connecting link 89. Thelower end of link 89 is pivotally connected at 90 to the outer swingingend of a crank arm 91 which in turn is keyed to an extension of valveshaft 13 exteriorly of the induction conduit 10.

Upon pivoting of crank arm 91, as for example by linkage 92 which issuitably connected with crank arm 91 and the customary pedal operatedthrottle mechanism, valve 12 is opened or closed. When crank arm 91 ispivoted clockwise, throttle valve 12 is progressively opened and link 39is moved downward to swing lever 86 counterclockwise, thereby to pivotlever 83 clockwise about the axis of shaft 70 and raise the point ofmovement limiting engagement between diaphragm 4t and cam 69. Inconsequence, upon opening of throttle valve 12 during increased engineload, the pumping stroke of diaphragm 4i and the fuel flow to fuel bowl16 are increased.

Upon counterclockwise or closing movement of valve 12 with decreasingengine load, lever 89 is moved upwardly, lever 86 is pivoted clockwiseabout the axis of pivot 87, and link 83 and cam 69 are pivotedcounterclockwise to the position shown in FIGURE 2 to minimize thepumping stroke of diaphragm 4t and the fuel supply to bowl 16.

FIGURE 3 is concerned with a carburetor, pumping mechanism, and throttleactuated linkage including crank arm 91, links 86 and 89, and yoke 85,as in FIGURE 2, but wherein lever 83 and cam 69 are eliminated. A pin 93slidable within yoke 85 in the manner of pin 84 of FIGURE 2 is securedto one end of a dog leg link 94 pivoted at 95 to a fixed bracket portion37a of housing 37. The other end of dog leg link 94 comprises a verticalyoke 96 having a pin 97 slidably retained therein. Pin 97 extendstransversely through a generally horizontal extending shaft 98 having atapered wedge cam 79 at its right end arranged to be inserted betweenlever 61 and cam 65. Shaft 98 is also slidably supported within bracketportion of housing 37a for horizontal movement.

Upon clockwise pivoting of crank arm 91 to open throttle valve 12, lever86 is pivoted counterclockwise as aforesaid, causing dog leg link 94- topivot clockwise and move wedge 79 between lever 61 and cam 65 to take upthe lost motion between lever 61 and enlargement 59 and thereby toincrease the effective pumping stroke of diaphragm 48. In this regard,the spring which urges upward pumping movement of diaphragm 40 will bedetermined so as to be in an unstressed condition when lever arm 61 isin the horizontal position illustrated. Thus diaphragm 41) will be atthe upper limit of its pumping movement when wedge 79 is at thewithdrawn position illustrated in FIGURE 3. As wedge 79 is movedrightward in FIGURE 3 upon opening of throttle 12 with increasing engineload, the effective pumping stroke of diaphragm 4t and the fuel suppliedto bowl 16 is increased.

Conversely as Wedge 79 is withdrawn leftward upon closure of throttle 12with decreasing load, the effective pumping stroke of diaphragm 4i andthe fuel flow to bowl 16 is decreased.

Having thus described my invention, I claim:

1. In a carburetor for an internal combustion engine having an intakemanifold system, a throttle valve in said system, a fuel bowl, amovable-wall type fuel pumping means, inlet conduit means connectingsaid pumping means and bowl for supplying the latter with fuel uponoperation of said pumping means, means for maintaining the fuel in saidbowl at a predetermined level comprising an overflow weir in said bowldefining at least in part a chamber adapted to receive excess fueloverflowing said weir from said bowl when the fuel in said bowl attainssaid predetermined level, fuel return means in communication with saidchamber to drain fuel therefrom upon overflow of excess fuel from saidbowl into said chamber, said pumping means having a reciprocable wallmovable in alternate intake and pumping strokes, a cyclical cam,follower means engageable with said cam and wall to effect reciprocationof the latter, and means operatively connected with said throttle valvefor adjustably controlling the relative positions of said follower meanswith respect to said cam to increase the length of said pumping strokeupon opening of said valve.

2. In a carburetor for an internal combustion engine having an intakemanifold system, a throttle valve in said system, a fuel bowl, amovable-wall type fuel pumping means, inlet conduit means connectingsaid pumping means and bowl for supplying the latter with fuel uponoperation of said pumping means, fuel duct means connecting said bowland intake manifold system for supplying fuel to the latter, means formaintaining the fuel in said bowl at a predetermined level comprising anoverflow weir in said bowl defining at least in part a chamber adaptedto receive excess fuel overflowing said weir from said bowl when thefuel in said bowl attains said predetermined level, fuel return means incommunication with said chamber to drain fuel therefrom upon overflow ofexcess fuel from said bowl into said chamber, said pumping means havinga reciprocable Wall movable in alternate intake and pumping strokes,adjustable movement limiting means engageable with said wall to limitthe length of the pumping stroke thereof, and means operativelyconnecting said throttle valve and movement limiting means to adjust thelatter to increase the length of said pumping stroke in accordance withthe opening of said valve.

3. In a carburetor for an internal combustion engine having an intakemanifold system, a throttle valve in said system, a fuel bowl, amovable-wall type fuel pumping means, inlet conduit means connectingsaid pumping means and bowl for supplying the latter with fuel uponoperation of said pumping means, fuel duct means connecting said bowland intake manifold system for supplying fuel to the latter, means formaintaining the fuel in said bowl at a predetermined level comprising anoverflow weir in said bowl defining at least in part a chamber adaptedto receive excess fuel overflowing said weir from said bowl when thefuel in said bowl attains said predetermined level, fuel return means incommunication with said chamber to drain fuel therefrom upon overflow ofexcess fuel from said bowl into said chamber, said pumping means havinga reciprocable wall movable in alternate intake and pumping strokes,pressure exerting means for yieldingly urging said wall in a pumpingstroke, reciprocable actuating means operatively connected with saidwall for moving the latter in opposition to said pressure exerting meansto effect an intake stroke of said wall upon movement of said actuatingmeans in one direction and for releasing said wall for movement in saidpumping stroke upon movement of said actuating means in the oppositedirection, and means operatively connected with said throttle valve foradjustably controlling the movement of said actuating means inopposition to said pressure exerting means for increasing said pumpingstroke in accordance with opening of said valve.

4. In a carburetor for an internal combustion engine having an intakemanifold system, a throttle valve in said system, a fuel bowl, amovable-wail type fuel pumping means, inlet conduit means connectingsaid pumping means and bowl for supplying the latter with fuel uponoperation of said pumping means, means for maintaining the fuel in saidbowl at a predetermined level comprising an overflow weir in said bowldefining at least in part a chamber adapted to receive excess fueloverflowing said weir from said bowl when the fuel in said bowl attainssaid predetermined level, fuel return means in communication with saidchamber to drain fuel therefrom upon overflow of excess fuel from saidbowl into said chamber, said pumping means having a reciprocable wallmovable in alternate intake and pumping strokes, pressure exerting meansfor yieldingly urging said wall in a pumping stroke, reciprocableactuating means operatively connected with said wall for moving thelatter in opposition to said pressure exerting means to effect an intakestroke of said wall upon movement of said actuating means in onedirection and for releasing said wall for movement in said pumpingstroke upon movement of said actuating means in the opposite direction,said actuating means including a cyclical cam and follower meansengageable with said cam to effect reciprocation of said wall, and meansoperatively connected with said throttle valve for adjustablycontrolling the relative positions of said follower means with respectto said cam to increase the length of said pumping stroke upon openingof said valve.

References Cited by the Examiner UNITED STATES PATENTS 2,136,959 11/1938Winfield 261-36 2,409,965 10/1946 Udale 261-36 2,734,729 2/1956 Loftin26136 2,977,099 3/1961 Ball 261-36 HARRY B. THORNTON, Primary Examiner.

1. IN A CARBURETOR FOR AN INTERNAL COMBUSTION ENGINE HAVING AN INTAKEMANIFOLD SYSTEM, A THROTTLE VALVE IN SAID SYSTEM, A FUEL BOWL, AMOVABLE-WALL TYPE FUEL PUMPING MEANS, INLET CONDUIT MEANS CONNECTINGSAID PUMPING MEANS AND BOWL FOR SUPPLYING THE LATTER WITH FUEL UPONOPERATION OF SAID PUMPING MEANS, MEANS FOR MAINTAINING THE FUEL IN SAIDBOWL AT A PREDETERMINED LEVEL COMPRISING AN OVERFLOW WEIR IN SAID BOWLDEFINING AT LEAST IN PART A CHAMBER ADAPTED TO RECEIVE EXCESS FUELOVERFLOWING SAID WIER FROM SAID BOWL WHEN THE FUEL IN SAID BOWL ATTAINSSAID PREDETERMINED LEVEL, FUEL RETURNS MEANS IN COMMUNIATION WITH SAIDCHAMBER TO DRAIN FUEL THEREFROM UPON OVERFLOW OF EXCESS FUEL FROMSAIDBOWL INTO SAID CHAMBER SAID PUMPING MEANS HAVING A RECIPROCABLE WALLMOVABLE IN ALTERNATE INTAKE AND PUMPING STROKES, A CYCLICAL CAM,FOLLOWER MEANS ENGAGEABLE WITH SAID CAM AND WALL TO EFFECT RECIPROCATIONOF THE LATTER, AND MEANS OPERATIVELY CONNECTED WITH SAID THROTTLE VALVEFOR ADJUSTABLY CONTROLLING THE RELATIVE POSITIONS OF SAID FOLLOWER MEANSWITH RESPECT TO SAID CAM TO INCREASE THE LENGTH OF SAID PUMPING STROKEUPON OPENING OF SAID VALVE.
 3. IN A CARBURETOR FOR AN INTERNALCOMBUSTION ENGINE HAVING AN INTAKE MANIFOLD SYSTEM, A THROTTLE VALVE INSAID SYSTEM, INLET CONDUIT MEANS CONNECTING SAID PUMPING MEANS, INLETCONDUIT MEANS CONNECTING SAID PUMPING MEANS AND BOWL FOR SUPPLYING THELATTER WITH FUEL UPON OPERATION OF SAID PUMPING MEANS, FUEL DUCT MEANSCONNECTING SAID BOWL AND INTAKE MANIFOLD SYSTEM FOR SUPPLYING FUEL TOTHE LATTER, MEANS FOR MAINTAINING THE FUEL IN SAID BOWL AT APREDETERMINED LEVEL COMPRISING AN OVERFLOW WEIR IN SAID BOWL DEFINING ATLEAST IN PART A CHAMBER ADAPTED TO RECEIVE EXCESS FUEL OVERFLOWING SAIDWEIR FROM SAID BOWL WHEN THE FUEL IN SAID BOWL ATTAINS SAIDPREDETERMINED LEVEL, FUEL RETURN MEANS IN COMMUNICATION WITH SAIDCHAMBER TO DRAIN FUEL THEREFROM UPON OVERFLOW OF EXCESS FUEL FROM SAIDBOWL INTO SAID CHAMBER, SAID PUMPING MEANSHAVING A RECIPROCABLE WALLMOVABLE IN ALTERNATE INTAKE AND PUMPING STROKES, PRESSURE EXERTING MEANSFOR YIELDINGLY URGING SAID WALL IN A PUMPING STROKEK RECIPROCABLEACTUATING MEANS OPERATIVELY CONNECTED WITH SAID WALL FOR MOVING THELATTER IN OPPOSITION TO SAID PRESSURE EXERTING MEANS TO EFFECT AN INTAKESTROKE OF SAID WALL UPON MOVEMENT OF SAID ACTUATING MEANS IN ONEDIRECTION AND FOR RELEASING SAID WALL FOR MOVEMENT IN SAID PUMPINGSTROKE UPON MOVEMENT OF SAID ACTUATING MEANS IN THE OPPOSITE DIRECTION,AND MEANS OPERATIVELY CONNECTED WITH SAID THROTTLE VALVE FOR ADJUSTABLYCONTROLLING THE MOVEMENT OF SAID ACTUATING MEANS IN OPPOSITION TO SAIDPRESSURE EXERTING MEANS FOR INCREASING SAID PUMPING STROKE IN ACCORDANCEWITH OPENING OF SAID VALVE.